Electrical induction apparatus



Jan. 8, 1929. 1,698,634"

1 S. E. JOHANNESEN 1.

ELECTRICAL mwcwrou APPARATUS Filed Jan. 24, 1923 Fi 3.1. I8 10 3 l6 /4- g I I veht 'P: Svend EJO hanne sen, y

AH i s AttoPn e Patented Jan. 8, 1929.

SVEND IE. JOHANNESEN, OF PITTSFIELD, MASSACHUSETTS, ASSIGNQR '10 GENERAL ELECT-RIC COMPANY, A CORPORATION OF NEW YORK I ELECTRICAL mnuerron renames;

Application filed January 24, 1928 Serial No. 249,159.

My invention relates to electrical induction apparatus such as transformers and reactors, and more particularly to an improved magnetic core construction for this'type of.

been so great as to make their general usev prohibitive. This disadvantage dueto greater cost of these alloys as compared with that of the silicon steel is partially offset, however, by the fact that the hysteresis and eddy current losses are substantially smaller. The general object of 'the present invention is to provide an improved magnetic core construction in w ich an expensive material having high permeability or low magnetic losses per unit volume and a less expensive material of comparatively lower permeability or higher magnetic losses per unit volume are both used with certain desirable advantages resulting from the combination.

The invention and its advantages will be better understood from the following description taken in connection with the accompanying drawing in which Fig. 1 shows.

" a transformer core constructed in accordance with the invention and provided with windings, a portion of the windings being broken away to reveal the construction more clearly, and Fig. 2 shows one of the core laminations.

Life reference characters indicate similar parts in both figures of the drawing.

The particular transformer shown in Fig. 1 includes a magnetic core having a central winding leg 10, two-outer legs 11 and 12 and yokes 13 connecting the three core" legs .at

their ends. The winding leg-:10 is surrounded by a low voltage winding 14 and a high voltage winding 15. The core is formed in two symmetrical halves which meet along 0 the axis of the winding leg 10. Each lamina-' tion of each half of the core isformed of a 'U-shaped element 16 and a straight element 17 joining the ends ofthe iU-shaped element.

The lamination elements 17 which form the 5 winding leg 10 are composed of the more exin magnetic losses.

pensive material having high permeabilit or'low magnetic losses per unit volumesucii as one of the well known nickel iron alloys having this property. The outer core legs 11 and 12 and the yokes 13, however, are composed of some less expensive and less permeable material such as silicon steel.

If the cross section of the winding leg 10 is twice that of each .outer leg and its yokes, then, neglecting any small leakage flux, the density of the magnetic flux will be uniform in the several core parts because all the flux flows through the winding leg but only half of it through either outer leg and its yokes. For a given loss in an core part, the cross section of the part, and therefore the amount of magnetic material used in the part may be substantially smaller if an expensivehigh permeability material is used than if a less expensive material hav ing lower permeability .is used. But the use of such expensive'material'in the outer 'core legs 1'1 and12 and in the yokes 13 is not justified because the much higher cost of the material is not nearly offset by reduced losses or the possible saving in the amount of material necessary. or both., The use of the better material in the winding leg 10, however, has further decided advantages' The smaller cross section of the winding leg permits the windings which surround itto be smaller so that not only are smaller'amounts of copper and insulation necessary for a given number of turns but the electrical losses in the'windings are reduced. The reduced size of windings in turn permits a reduction in the lengths of the outer core parts including the outer\ core legs 11 and 12 with their yokes 13 so that here also there is a. saving in material and also a reduction From the preceding description of the invention' andits advantages, it will be apparent that decided savings in material and improvement in efliciency practically through-f out the transformer structure results from the useof magnetic. material having high permeability or low losses perunit volume inthe winding leg or core part surrounded by a winding or windings. It will also be apparent-that there is ample "roomi for any desired cross section of the outer =core parts including the outer core legs 11 and 12 and their yokes 13 without afiecting in any way the-amount of material or the electrical and magnetic efficiencies in the winding leg and in the windings. The use of the better and more expensive material in these outer core parts is therefore not justified because the comparatively small advantages secured aremore than offset by the much greater cost of this material as compared with a less expensive material having lower permeability or higher losses per unit volume. As indicated in the drawing, the cross section of the highly permeable winding leg may be considerably smaller than the combined cross sections of. .the two less permeable outer core parts which connect the ends of the winding leg.

The invention has been explained by describing and illustrating one. particular application thereof but it will be apparent that various changes may be made within the scope of the invention as defined by the appended claims.

Vhat I claim as new and desire to -secure by Letters Patent of the United States is:

1. Electrical induction apparatus including a magnetic core, and a winding surrounding a part of said core, the core part surrounded by said winding including material having lower magnetic losses per unit.

- volume than material in other core parts outside said winding.

2. Electrical induction apparatus including a magnetic core, said core being formed of parts having and magnetic material connecting the ends of said" winding leg, and a winding surrounding said winding leg, the cross section of said winding leg being smaller than the total cross section of said material connecting its ends, and the winding leg being formed of material having a permeability higher than that of the magnetic material connecting its ends.

Electrical induction apparatus including a magnetic core having a winding leg and a plurality of outer legs connected to the ends of said winding leg, and a.winding surrounding said winding leg, said winding leg having higher permeability than that of said outer legs.

In witness whereof, I have hereunto set i my hand this 21st day of J an., 1928.

SVEND E. JOHANNESEN.

DISCLAIMER Pitts-field, Mass.

ELECTRICAL INDUCTION APPA- 8, 1929. Disclaimer filed September 12, 1929 Electrw Company.

subject matter of claims 1, 2, and 5 

